This invention relates to injection molding and more particularly to a hydraulically actuated valve gated system having improved actuating mechanism.
Hydraulically actuated systems are known in the art and examples are disclosed in the applicant's following U.S. patent applications, Ser. No. 399,770 now U.S. Pat. No. 4,433,969 filed July 19, 1982 entitled "Injection Molding Valve Pin Bushing and Method"; Ser. No. 446,460 filed Dec. 3, 1982 entitled "Injection Molding Core Ring Gate"; and Ser. No. 470,192 now abandoned filed Feb. 28, 1983 entitled "Injection Molding Hollow Tip Ring Gate", and the applicant's Canadian application Ser. No. 398,866 filed Mar. 19, 1982 entitled "Hydraulically Actuated Injection Molding System". While these previous hydraulically actuated systems are suitable for many applications, there has been found to be considerable resistance to them due to difficulties experienced in installation. In particular, expensive precision drilling equipment is required to accurately drill lengthy hydraulic fluid supply lines through the back plate in which the hydraulic cylinder is located. Otherwise, there is a danger the hole will stray off-line into the cylinder cavity and ruin the back plate. Therefore, it is desirable to provide an alternative structure whereby the user has the option of not drilling the hydraulic supply lines through the back plate. Furthermore, in order to improve pressure distribution, it is advantageous that the hydraulic fluid be introduced at more than one point on either side of the piston.